<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
  <style>
    #d1{
      width: 100px;
      height: 100px;
      border:1px solid red;
      /*单独某个方向添加外边距*/
      /*margin-right: 100px;*/
      /*margin-top: 50px;*/
      /*四个方向添加外边距*/
      margin: 50px;
      /*上下和左右添加外边距*/
      margin: 100px 50px;
      /*上右下左 顺时针赋值*/
      margin: 10px 20px 30px 40px;
    }
    #d2{
      width: 100px;
      height: 100px;
      border: 1px solid red;
      /*上下相邻两个元素彼此添加外边距, 取最大值*/
      margin-top: 50px;
    }
    #s1{
      /*行内元素上下外边距 无效*/
      margin-right: 50px;
    }
    #s2{
      /*左右相邻彼此添加外边距 两者相加*/
      margin-left: 30px;
    }
  #big{
    width: 200px;
    height: 200px;
    background-color: green;
    /*解决粘连问题*/
    overflow: hidden;
  }
  #big>div{
    width: 50px;
    height: 50px;
    background-color: blue;
    margin-left: 50px;
    /*当元素的上边缘和上级元素的上边缘重叠时,给元素添加上外边距会出现粘连问题,
    给上级元素添加overflow:hidden解决*/
    margin-top: 50px;
  }
  body{
    margin: 0;
  }
  </style>
</head>
<body>
<h1>这是h1</h1>
<p>这是p</p>
<ul>
  <li>aaa</li>
  <li>bbb</li>
  <li>ccc</li>
</ul>
<div id="big">
  <div></div>
</div>
<span id="s1">span1</span><span id="s2">span2</span>
<div id="d1"></div>
<div id="d2"></div>
</body>
</html>